Electric-iron plug



Feb. 22, 1927.

1,618,686 B. e. c. STEPHENS ELECTRIC-IRON PLUG Filed Jan. 50, 1925 3e; zm/n/ 66075 mule flie/lny/f v l/fa r o Patented F b. 22, 1927.

UNITED I STATES f 1,618,686- PATENT OFFICE.

BENJAMIN GEORGE CLAUDE STEPHENS, 0F AUCKLAND, NEW ZEAIiAND.

ELECTRIC-IRON PLUG.

Application filed January 80, 1925, Serial No. 5,753, and in New Zealand September 19, 1924.

This invention relates to the ordinary types of plugs used in conjunction with electr1c irons for the attachment of the cord conductor wires thereto, and which plugs in theirgeneral form are made with two contact sockets that respectively fit on to resistance terminal pins upon the iron.

'The invention has been devised with the object of embodying means within such a .form of plug that will cause the current to. the iron to be automatically cut off should. the iron become overheated through neglect or any other cause; These means are of such a nature that a switch interposed in the conductors to one of thecontact sockets, remains closed so long as the usual and safe temperatures are not exceeded, but which switchis positively opened immediately the temperature reaches the degree predeter: mined upon and for which the appliance is set.

The said switch is adapted to be controlled by a bi-metallic stri composed on the well known principle 0 strips of laminated metals having diifere'nt oo-efiicients of expansion and contraction and which strip is disposed within the plug so that one end is made fast to'and in thermo contact with one of the contact sockets. The heat from the iron will thus be conveyed by contact conductivity to the stri to cause its free end 'to move laterally s ould the heat become 'suflioiently great.

Inits normal state the free end of the strip holds a spring controlled switch in place to keep the circuit closed, but when such endmoves later-all for al'specified distance, it

frees the switc so thatthe spring may actu-- tive, a construction of the spring controlled switch the features of which provide for the automatic testing of the thermostatic control in that the switch is designed to opena short period after the iron current is turned on and then is manually closed again and held closed so longas the ordinary working temperature isnot exceeded.

A suitable manner of carrying out the invention is illustrated in the accompanya in drawings, in which igure' 1 is a front elevation of the plug.

Figure 2 is a face view-of the rear or base half of the plug showing the fittings attached thereto.

Figure 3 is a side elevation of the plug, the

wallbeing broken away to expose the fit tings.

1Figure at is an underneath plan of the 1) ug. I

Figure 5 is a horizontal section thereof, taken on the line 5-5 of Figure 2.

Figure 6' is adetail view of one of the sockets and certain attached parts.

Figure 7 is a detail view showing in elevation, the switch as made in the alternative manner mentioned, and in its first closing position.

Figure 8. is a similar view, partly in section, showing the switch in its second closing position.

Figure 9 is a plan thereof.

The plug is formed upon theusual general lines prevailing in the construction of these appliances; that is, with a body of vulcanite or other insulating material made in two halves, a near or base half 7 and a front half or cover 8, constructed to fit face to face together and to be fastened'by means of transversely extending screws 9. The adjacent faces .of these two parts are recessed to receive the several fittings embodied in the plug and these comprise two socket tubes 10 and 11 that extend upward from openings 12 in the lower end of the plug and are secured to the rear half 7 thereof by screws 13. These sockets are made in the usual split style to adapt them for passing respectively over the terminal pins of the electric iron. and for ripping them.

Tie socket 10 is connected with a conductor strip 14 leading to the upper end of the plug and which is secured 'to the plug at its upper end by means of a terminal screw pin 15 to which also one wire of the ordinary cord 16 is connected.

The second socket 11 is also connected with a conductorstrip 17 but this-strip is made in two portions, an upper portion 18 being provided and affixed to the plug so. that its lower end overlaps thetop of the portion 17 with a distance between. The said up per portion 18 is secured by means of a terminal screw 19 to which the second wire of the cord 16 is connected. Solong therefore as the gap between the portions 17 and the iron.

A switch lever 20 is provided and is pivoted in a frame bearing 21 aflixed to the rear half of the plug. This lever extends across the width of the plug and at its inner end has ailixed to it a metallic bridging block 22 which is so shaped as to be adapted to pass in between the ends of the two portions' 17 and .18 of the second conductor strip and to bridgethem electrically, or to disengage said portions and thus break the contact. The lever tends to rock in a direc tion ;to effect such disengagement, due to the action of a spring 23 (Figure which surrounds the pivot pin 24 of the lever and bears upon the inner arm ofsaid lever, or'

. to other equivalent means.- When the lever is freed, thisspring will act and-rock the leverto open the switch formed thereby.

"The other endfof the lever passes out through a slot 25 formed'in the joint between the two plug halves and is made with" a' finger knob 26 onits end so-that it'may be actuated from the outside to close the switch. When thelever is in the closed position, the knob 26 lies within a hood 427 formed in the plug edge to receive it and to protect it against being accidentally engaged to turnthe switch, in the use of theiron.

I The lever and its bearings are effectively insulated from; the conductor strip 14 to prevent anyj'short circuitingthrough the lever,- or the lever. may be itself formed of non-conducting material.

The lever SWlt-ChQlSqlGtfilIlGd in its raised position to close the circuit by means of the bi-metallic strip -'30 }'that is positioned to extend up within one edge of the plug so that its u penendengages beneath. the

' bridging afiixed ybraz'ing or like operation to a copperor other metallic bracket piece 31!v This bracket piefce is shaped to extend across the rear and across the outer side of the socket 11 and also has the-socket made'fast to it so thata thermo unit is produced comlever to break the contact.

posed of the socket, the bracket and the strip 30. The strip 30 is also so disposed that its upperend is adapted to move across the width of the plugin the movements- .towhich it-is'subject under varying heat conditions. p 1

The bi-m'etallic strip 30 is so made that bending movement takes place when the strip is subjected to a heat greater than that of the usual, working temperatures of the iron. Should the temperature of the iron therefore increase abnormally, the heat is conveyed by direct contact from the iron ter minal pin to the socket 11 and from it to the strip 30. The strip will then bend outward, freeing'the bridge block 22 and'permitting the spring 23 to act and rock the The current will thus cease to flow.

' Accurate adjustment ofthe amount of.

movement in the strip necessary to free the block 22 is obtained by means of the small adjusting screw 33 passing through one por- 4 tion of the bracket piece 31 and engaging book 22 while its lower end is the outside face of the strip ate-point above the strips attachment to such bracket piece. Asmall aperture 34 is left in the joint between the' two halves of the plug to permit oflaccess to this screw.

' In the construction'of the switch lever '20 shown in igures 7 to 9, its bridging end 22 is forked, and between the fork arms a tumblerpiece 35 is pivoted upon a pin 36. 'Such tumbler-piece has a downwardly extending nose 37 on its outer end. and is so constructed and pivoted that the inner end.

is. adapted to fall and to project the nose ties of the fork arms 22 of the switch lever. The tumbler piece is prevented from falling .too far at-its'inner end by means of a pin 38 extending across the fork arms of the 'switch lever, and the amount of fall to be allowed it may be accurately adjusted by means of the screw pin'39 that is screwed down through such end to engage the said cross-pin 38. Y

The thermostatic'strip 30 is made on its inside face with'atooth 30 positioned near its top end, such tooth havin a square upper end and an inclined inside face. The

strip in this case is made so thatits upper end will bend outwards a small amount as the iron heat works up to its safe working heat, as for instance after a'period often or fifteen minutes from turningon the cur- 37 out a short distance beyond the extre'mi- 3,

rent, and 'will bend further out as the heat exceeds .the predetermined safety point.

' When the iron is cold and the switch 20 is closed, the ends of the fork arms 22 of the switch lever as they pass up, will brush aside the top of the strip 30 and will rest-on such top,'the nose 37 of the tumbler piece engaging the face of the tooth 30 and being turned in thereby, as in Figure 7. As the iron heats and thestrip 30 turns out/ it will free the switch lever, so that the switch will open in the manner before described." Then 'on'closing theswitch manually, with the strip still in its partially bent' position, the nose 37 which has fallen outwards owing to the dropping ofthe tumbler piece, wi1l. engage and left and forgotten, while the second control ensures that nooverheating'through neglect or other cause will take place after-the iron has been heated to its working temperature.

The thermostatic strip 30 may have attached to it, a pin'40 that projects trans- =versely from its outer surface through between the body parts 7 and 8 to the outside end of said lever; a spring tending to swing abnormally heated.

said lever into non-bridging position; and

'a thermostatic element adapted to engage and retain the lever in bridging position and to automatically disengage the same when 2. In an electric switch, the combination of a conductor; a pivotally-mounted switch leverhaving a forked end adapted to engage said conductor; a spring tending to swing said lever end away from the conductor; a

tumbler pivotally mounted in the lever fork for automatic movement independently of and relatively to said .lever; and a thermostatic element having a tooth adapted to engage said tumbler and thereby retain the lever in conductor-engaging position, and to automatically release the tumbler when abnormally heat-ed.

3. An automatic switch, according to claim 2, in which the tumbler has a depending nose that normally projects beyond the forked end of the switch lever and is adapted to be directly engaged and disengaged by the tooth on the thermostatic element,

4. An automatic switch, according to claim 2, in which the tumbler carries an adjustable stop for engagement with a cross-pin mounted in the forked end of the switch lever to limit the pivotal. movement of the tumbler in one direction.

5. An automatic switch, according to claim 2, in which the tumbler is provided at one end with a depending nose and at the other end with an adjustable depending stop; said nose normally projecting beyond the forked end of the switch lever and adapted to be directly engaged and disengaged by the tooth on the thermostatic element; and said stop adapted for engagement with a cross-pin mounted in the forked end of the switch lever to limit the pivotal movement of the tumbler in one direction.

In testimony whereof, I afiix my signature.

BENJAMIN GEORGE CLAUDE STEPHENS. 

